Means for tuning short-wave hollow-body resonator apparatus



July 6, 1943. A. H. RYAN 3, MEANS FOR TUNING SHORT-WAVE HOLLOW-BODY RESONATOR-APPARATUS Filed Aug. 1a, 1940 I Fiy. 1.

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WITNESSES: I INVENTOR Alden fl BY 5 ,3 22 14:! ...J

ATTORNEY Patented July 6, 1943 MEANS FOR TUNING SHORT-WAVE HOL- LOW-BODY RESONATOR APPARATUS Alden H. Ryan, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 13, 1940, Serial No. 352,412

4 Claims.

..My invention relates to high-frequency or short-wave electrical apparatus, and it has particular relation to such apparatus utilizing conductor-ensheathed hollow-body resonators, operating at wave lengths of the order of 40 centimeters, or between the limits of one centimeter and five meters, more or less. Still more particularly, my invention relates to novel means for tuning the same. --The resonant frequency of a hollow-body resonator depends upon its shape, its physical dimensions, and the mode or manner of its oscillation. Tuning of such hollow-body resonators may be effected by means of putting large accordion-pleated, expansible and contractable, thin-walled metal annular members in a portion of the cylindrical wall of a cylindrically shaped resonator, for changing the axial length of the cylinder.

In accordance with my invention, the afore said method of tuning is utilized in an electronic device in which an electron-beam is passed axially through two such cylindrically shaped resonators, disposed back-to-back, with a shorter cylindrical member disposed inside of the same, so that the electron-stream is first velocity-modulated as it passes through an opening in the end-wall of the first resonator, and then through the first end of the inner cylinder, the electrons of the velocity-modulated stream becoming bunched in their transit through the inner cylinder, and finally giving up some of their energy as they pass out of the second end of the inner cylinder and through an opening in the end-Wall of the second resonator.

An object of 'my present invention is to avoid 'difliculties which have been experienced in moving the end walls of the resonators toward and away from the respective ends of the inner cylinder, which has resulted in a change in the transit-time required for the passage of the electrons through the intervening portions of the respective resonators, thus lowering the efiiciency of the apparatus. The aforesaid tuning-method has also involved a disadvantage because of the large size of the flexible-Wall portion which was needed in order to efiect the change in longitudinal dimension, making it diificult to maintain a vacuum in the device or to outgas the device, when it is being originally assembled, without overheating the thin wall-parts in the process.

It is a further object of my invention to provide means for changing the tuning of such resonators Without disturbing either end-wall, and

without requiring large-size flexible-wall members for effecting the tuning. a v It is also an object of my invention to provide a high-frequency hollow-body resonator having. a re-entrant wall-portion'defining a restricted space-portion between two relatively closely spaced wall-portions, as compared to other dimensions of the resonating-space, in acombination' utilizing an externally controllable movable means for changing the efiective capacity between said two relatively closelyspaced wall-por-v tions, as a means for tuning the resonator, andin combination, also, with coupling-circuit means for coupling the internal oscillations within said resonator to some external device.

Another object of my invention is to providemeans such as that just described, in an electrontube device in which an electron-beam is modu-; lated and controlled with the aid ofa tunable resonator of the'type just described.

With the foregoing and other objects in view, my invention consists in the apparatus, structures, combinations, systems'and methods here: inafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure 1 is a, diagrammatic horizontal sectional view of an exemplary form of embodimentof apparatus embodying my invention, with a dia-' grammatic representation of external circuits and apparatus for utilizing the same; and

Fig. 2 is a vertical sectional view on the plane indicated by the line IIII in Fig. 1.

The form of embodiment of my invention'as illustrated in the drawing consists of an evacuated metal container comprising an elongated cylindrical wall-portion 4 andtwo hermetically joined end-wall portions 5 and 6,respectively. Disposed within the cylinder 4 is a centrally disposed metal partition-wall l which is in turn provided with a central opening 8 in which is se-i cured a smaller metal cylinder 9 having open ends H and 12, respectively. Disposed between the inner cylinder end II and the first end-wall 5 of the outer cylinder, is a metal partition-member 53 which is provided with a central opening [4 in alignment with, and closely spaced from, the end-opening H of the inner cylinder 9. A similar metal partition-wall I5 is provided at the other end of the device, between the inner-cylinder end I2 and the end-wall'fi of the outer cylinder, said partition-wall I5 being provided with a central opening 16 in alignment with, and closely spaced from, the end opening l2 of the inner cylinder 9. The intervening space between the two openings I 4 and ll constitutes apart of a larger resonating-space I8 which extends between the two cylinders 4 and 9 and between the two partitions l3 and 7. In like manner, the intervening space between the two openings I2 and I6 constitutes a part of a second resonatingspace I9 which extends between the two cylinders 4 and 9 and between the two partitions I and I5.

In the illustrated form of the invention, means are provided for producing an electron-beam which passes successively through the central openings I4, II, I2 and I6. The beam-producing means includes a source of emitting electrons which is illustrated as a filament 2| disposed in the space between the end-wall 5 and the first partition I3. Said filament 2| is provided with terminal-leads 22 and 23 which extend out of the casing through vacuum-tight insulating bushings 24 disposed in the end-wall 5.

In order to make it possible to maintain the 4 are focused into a beam as they pass through the first partition-opening l4, or any more elaborate focusing-means may be utilized, as is well known in the art of electronic apparatus. The electrons in this portion of the beam are also accelerated by means of a voltage-difierence which is supplied by means of an adjustable battery 25, which is connected between a grounded point 26 of the outer casing, and one of the leads 23 of the filament 2|. In passing through the first intervening space between the first two central openings I4 and II, the electron-beam is subjected to the velocity-modulating influence of the electrostatic field-portion of the oscillations within the first resonating space I8. The velocity-modulated electron-beam then passes into a second intermediate space between the opposite end-openings II and I2 of the inner cylinder 9, thus providing what is known as a drift-space in which velocity-modulated electrons may have an opportunity to become bunched, so that the first resonating space I8 is commonly known as a buncher,

The bunched electrons emerge from the third central opening I2 into the intermediate space between the third and fourth openings I2 and I6, which space is a part of the second resonating space I9, which is commonly known as a catcher, because it absorbs some of the energy of the bunched electrons, the successive bunches or impulses of electrons occurring at a high-frequency rate corresponding to the resonant frequency of the catcher I9, so as to increase the internal oscillations therein.

The electron stream finally leaves the last opening I6 and enters the last compartment of the device, between the partition I 5 and the endwall 6, where the electrons are finally dissipated or collected on the walls of said space. An electron beam deflector is shown, in the form of a floating or insulatedly mounted electrode 30 of carbon or other material having a secondary electron-emissivity ratio materially less than unity, as is described and claimed more particularly in a copending application of G. L. Tawney, Serial No. 323,935, filed March 14, 1940, and.

assigned to the Westinghouse Electric & Manufacturing Company.

The illustrated apparatus also includes an external-circuit exciting-device for exciting the internal oscillations of the first resonator-space I8 from some source outside of said space, said means being illustrated in the form of a feedback means from the catcher resonator-space I9. The feedback means is illustrated as a magnetic coupling device including half-loop 3| and 32 terminating on opposite sides of the central partition I and including an intermediate conductor 33 joining said loops, said conductor 33 passing, in spaced relation, through a suitable opening 34 in the central partition I.

In accordance with a preferred form of embodiment of my present invention, I provide a tuning means in the form of means for in effect changing the capacitance between the spaced Wall-portions containing the openings I4 and II, and between the spaced wall-portions containing the openings I2 and I6, To this end, externally controllable movable means must be provided, associated with the intervening spaces in question. A preferred means for effecting such a control, as illustrated, comprises a narrow auxiliary electrode 35 and 36, one for each of the intervening spaces to be controlled, each of said auxiliary electrodes, such as the electrode 36, being movable in and out, through a slotted opening 3'! in the outer cylindrical wall 4. Disposed outside of the cylindrical casing-wall 4, so as to cover the elongated slot 31, is a hermetically joined flexible-walled protuberance 38, which has thin flexible metal walls pleated like an accordion, so that the end 39 of the protuberance can be moved in and out, toward and away from the cylindrical housing-member 4. The outer end of the movable electrode 36 is hermetically joined to the end-wall portion 39 of this flexible protuberance 38, and an extension 40 of said movable electrode 36 is disposed on the outside of the protuberance 38 for the purpose of securing an external control of the position of the auxiliary electrode 36. In the form of my device which is illustrated, the extension 40 is intermediately pivoted to a lever II which is pivoted, at one end, to a lug 43 on the cylindrical enclosure-member 4, and which is adjustable, at the other end, toward and away from the cylindrical enclosure 4, by means of a set screw 44 which may be mounted in a bracket 45.

In operation, the movable tuning electrode 38 is disposed in the space between the partition I5 and the end I2 of the inner cylinder 9, and said movable tuning electrode 36 extends down to the vicinity of the longitudinally extending line joining the edges of the openingsIZ and I6, so that it extends to the vicinity of the edgeportion of the electron-beam. The tuning electrode 36 is electrically connected to an extension of the wall-portion or partition I5 which is provided with the opening I6, so that, as the movable tuning electrode 35 is moved in and out, it

- changes the electrostatic coupling with the end of the inner cylinder 9. The effect of this change is to strongly change the resonance-frequency of the catcher resonator-space I9. In a similar manner, the other movable tuning electrode 35 controls the tuning of the buncher resonator-space I8.

When the filament 2I is heated, and when a suitable voltage, from 500 volts to 5,000 volts, is applied thereto for the purpose of accelerating the electrons, an electron beam is established which is modulated in the first intervening space between the openings I4 and H of the buncher l8, and which gives up some of the energy of the bunched electrons in the catcher intervening space between the openings l2 and I6. Some of the oscillation-energy of the catcher I9 is taken off, in a coupled output-circuit which is illustrated as comprising a half-loop 41 terminating on the inside of the partition I5, within the second resonating-space l9, and having a terminal conductor-portion 48 which extends out through an opening 49 in the partition l5, and which is connected to an external conductor which extends out of the casing, through a vacuum-sealed insulating bushing 52, and is connected to some external apparatus utilizing the high-frequency energy, such as an antenna 53.

My novel tuning-electrodes 35 and 36 make it possible to quickly and minutely control the output-frequency, even while the device is in operation.

In the illustrated form of embodiment of my invention, the four central openings I4, I I, I2 and iii are covered or closed with grids 54,

55, 56 and 51, respectively, said grids being illustrated symbolically as metal-wire screens, although such illustration is intended to be symbolic of any open-work grid-construction which is known in the art of electron-tube control. I desire that the terms opening and grid shall be construed to be synonymous with each other,

and interchangeable, either one designating either a single opening or a plurality of juxtapositioned openings.

While I have described my invention in a single preferred form of embodiment, I desire it to be understood that said form of embodiment is only illustrative, anad that various changes may be made in the precise details of construction and arrangement, without departing from the essential idea of the invention, at least in its broader aspects. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. An electron-discharge apparatus comprising an evacuated container; means therein for producing an electron-beam; a modulating beamcoupling means for operating on said electronbeam at one region thereof for modulating said beam at a predetermined high-frequency rate; an excitable beam-coupling means to be acted upon by said electron-beam at another region thereof for absorbing high-frequency energy from the modulations of said beam; said beamcoupling means including hollow-body resonatormeans to be excited to oscillate at a common resonating-frequency and including frequencychanging means for adjusting said common resonating frequency, said frequency-changing means including an externally controllable movable means adjacent to the path of said beam for varying the capacity-effects in its vicinity without changing the effective extents of said beam-coupling means along the path of said beam; coupling excitation-means mounted in said hollow-body resonator-means for supplying high-frequency excitation-energy to said modulating beam-coupling means; and coupling output-means mounted in said hollow-body resonator-means for deriving high-frequency electrical energy from said excitable beam-coupling means.

2. An electron-discharge apparatus comprising an evacuated container; means therein for producing an electron-beam; a first hollow-conduc tor means for providing a resonator-space, to be traversed by said beam for producing a high-frequency potential-gradient for acting longitudinally upon said beam at a predetermined region thereof; means providing a drift-space to be traversed by said beam after its passage through said predetermined region; and a second hollowconductor means for providing a resonatorspace, to be traversed by said beam issuing from said drift-space, said second hollow-conductor means being adapted to be excited at a resonantfrequency by the high-frequency modulations in said beam and including coupling means coupled thereto for deriving high-frequency electrical energy from the oscillations therein; said two hollow-conductor means having a common resonating-frequency and including frequencychanging means for adjusting said common resonating frequency, saidfrequency changing means including an externally controllable movable means adjacent to the path of said beam for varying the capacity-effects in its vicinity without changing the lengths of the paths to be traversed by the beam in passing through the respective resonator-spaces.

3. A high-frequency resonator comprising an evacuated container; means therein for providing a source of electrons; four successively mounted, spaced grids therein providing a first intervening space between the first and second of said four grids, a second intervening space between the second and third of said four grids, and a third intervening space between the third and fourth of said four grids; an electron-beamproducing means; and hollow-body resonatormeans, including said first and third intervening spaces, for utilizing said first and third intervening spaces, in effect, as parts of a buncher and a catcher, respectively, whereby the electrons of said beam are velocity-modulated as a result of the high-frequency resonating electrostatic field in said buncher, and whereby the bunched electrons of said electron-beam yield some of their energy to the high-frequency oscillations within said catcher to supply excitation-energy thereto; said hollow-body resonator-means having a common resonant oscillation-frequency for said buncher and catcher operations, respectively, and including frequency-changing means for adjusting said common resonant oscillation-frequency; said frequency-changing means including an externally controllable movable means in spaced juxtaposition to at least one of said four grids for adjusting the efiective capacity between said grid and its associated grid in the hollow-body resonator-means without changing the distance to be traversed by the beam between said grid and its associated grid, whereby the resonatingfrequency of said hollow-body resonator-means may be controlled.

4. A high-frequency resonator comprising an evacuated container; means therein for providing a source of electrons; four successively mounted, spaced grids therein providing a first intervening space between the first and second of said four grids, a second intervening space between the second and third of said four grids, and a third intervening space between the third and fourth of said four grids; an electron-beamproducing means; means in said container providing, in effect, at least two separate hollowbody resonators, the first of said hollow-body resonators including said first intervening space within its resonating space for operating as a buncher for velocity-modulating the electrons of said beam, and the second of said hollow-body resonators including said third intervening space Within its resonating space for operating as a catcher for increasing its oscillation as a result of the bunched electrons, most of the space of at least one of said hollow-body resonators including hollow-space dimensions larger than the grid-spacing of its intervening space, said one of the hollow-body resonators also including frequency-changing means including a movable auxiliary conductor-member movably adjustable in the vicinity of said intervening space for tuning the resonator without changing the aforesaid grid-spacing of the associated intervening space, and coupling means for coupling the second one of said resonators to some external device.

ALDEN H. RYAN. 

